Medical catheters are used for the administration of therapeutic agents or nutrients into a body of a patient. A medical catheter is inserted into the body and, more particularly, either into a moderate to large vessel within the body or a body cavity or space. The catheter includes an exit port to deliver a solution, which may include nutrients, therapeutic agents, or a combination thereof from a lumen of the catheter to the body.
Conventional catheters include at least one pressure responsive valve, such as a slit valve. A slit valve may, for example, be formed by cutting one or more slits in a wall of a catheter. The pressure responsive valve opens in response to pressure gradients to permit fluid flow through the catheter. More specifically, when the pressure differential exceeds a threshold of the slit valve, the catheter walls defining the slit protrude and allow fluid to flow through the catheter.
Depending on whether the pressure differential is negative or positive, fluid may travel from the patient to the catheter or from the catheter to the patient. A negative pressure differential occurs when the pressure level inside the catheter decreases below the pressure level outside of the catheter. A slight negative pressure differential tends to close the slit, however a larger differential causes the slit to open inward. A positive pressure differential occurs when the pressure level inside the catheter increases above the pressure differential outside of the catheter. A positive pressure differential opens the slit outward.
At neutral pressures, i.e., the pressure level inside and outside of the catheter are substantially the same, the catheter walls defining the slit form a seal to prevent fluid flow into or out of the catheter. In other words, the catheter closes at neutral pressures. The pressure differential needed to open the slit valve may vary depending on the number of slits in the catheter, the length of the slits, the thickness of the catheter wall or the elasticity of the catheter wall.
Some patients may require an implanted catheter for an extended period of time. However, catheters that remain implanted in a body of a patient may become occluded over time due to blood ingression, thrombus formation or fibrous tissue encapsulation. When a catheter does become occluded, the patient will not receive the necessary therapeutic agents or nutrients. In this case, the catheter must be removed and either cleaned or replaced with a new catheter.